Prince Gustav Ice Shelf
Prince Gustav Ice Shelf was the most northerly ice shelf on the Antarctic Peninsula, and it was the first to collapse in 1995. It shrank progressively throughout the second half of the 20th Century, before collapsing to leave open water between James Ross Island and Trinity Peninsula1. Anecdotal evidence suggests that in the early 20th Century it was connected to an enlarged Larsen A Ice Shelf, and that it had been shrinking and thinning for many decades prior to collapse.
Following the collapse of Prince Gustav Ice Shelf, tributary glaciers were observed to accelerate, thin and recede back even 15 years after collapse2,3, directly contributing to eustatic sea level rise.
Larsen Ice Shelf
The Larsen Ice Shelf actually comprises four ice shelves; Larsen A, on the north-eastern Antarctic Peninsula, Larsen B, south of Seal Nunataks (Larsen A and B have both collapsed), Larsen D, the large currently remaining ice shelf, and Larsen D, the long, thin ice shelf fringing the south-eastern Antarctic Peninsula.
Larsen A, close to Prince Gustav Ice Shelf, used to extend from Cape Longing to Robertson Island, and merged with Larsen B at Seal Nunataks. Larsen A was relatively stable and around 4000 km2 from 1961 until the 1980s, when periodic large calving events resulted in stepwise recession1. Larsen B underwent rapid calving and disintegration in 2002, when most of the ice shelf was lost1. Their collapse follows thinning both from basal melting and surface summer meltwater formation4. This recession began in the 1980s. Larsen C is also currently thinning5. Larsen B has been thinning throughout the Holocene6, but its recent collapse was unprecedented during the Holocene.
Following the collapse of the Larsen ice shelves, their tributary glaciers were observed to accelerate, thin and recede, resulting in a direct contribution to global sea level7.
Larsen C has been stable over the last few decades, a but a large and growing rift across the ice front is threatening to extent all the way across the ice shelf. This would calve the largest iceberg ever recorded, and could destabilise the ice shelf.
Wordie Ice Shelf
Wordie Ice Shelf is made up of six major glacier units that flow into it, and there are around 20 ice rises and ice rumples8. Wordie Ice Shelf disintegrated in a series of calving events during the 1970s and 1980s, and by 1992 was little more than a few disconnected glacier tongues1. This dramatic collapse could have been caused by warm summer air temperatures, which increased summer surface ablation9. Ice rises on the ice shelf, where the ice shelf is pinned to bedrock lumps on the sea floor, may have aided the ice shelf’s stability between large calving events1.
Wilkins Ice Shelf
Wilkins Ice Shelf is the largest ice shelf in West Antarctica that is currently undergoing rapid shrinkage. Recession has occurred through a series of rapid calving events, where it calved a number of large, tabular icebergs 1. Significant break-ups occurred in 1998 and March and July 2008, and finally again in April 2009. The overall area was reduced to 5434 km2, which is around two thirds of its original size.
Wilkins Ice Shelf flows only slowly, at around 30-90 metres per year (the nearby Wordie flows at 200-2000 metres per year). It has a catchment area of 16,900 km2, which is a small area of grounded ice to nourish an ice shelf, and it is sustained largely by in situ accumulation1. Melting on the Wilkins Ice Shelf is largely by basal melting and some surface melting in the summer10. The Wilkins Ice Shelf is thinning at a rate of 0.8 metres per year (1992-2008), which is driven by a basal melt rate of 1.3 ± 0.4 metre per year11. On slow-moving, thin, near-stationary ice shelves like the Wilkins Ice Shelf, basal melting rapidly melts away the original glacier ice within a few kilometres of its grounding line12. According to Rignot et al. (2013), the Wilkins Ice Sheet loses 18.4 ± 17 gigatonnes of meltwater each year as a result of basal melting, and 0.7 ± 0.4 gigatonnes of ice per year following iceberg calving.
You can explore these ice shelves using the Google Map below. Note the mountains running down the length of Alexander Island. George VI Ice Shelf lies between Alexander Island and the mainland Antarctic Peninsula (Palmer Land). On the west of Alexander Island, you have the Wilkins Ice Shelf and several smaller ice shelves. Can you see where the ice shelf starts? Look for a break in slope to see where the glacier ice starts to float.
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George VI Ice Shelf
George VI Ice Shelf is an unusual ice shelf that is trapped between the mainland (Palmer Land) and Alexander Island. Ice flows from the mainland north and south to the marine termini at either end of Prince Gustav Channel. George VI Ice Shelf is located on the -9°C annual isotherm (mean annual air temperature is -9°C), which has been proposed as the theoretical limit for ice-shelf viability13.
George VI Ice Shelf measures 24,000 km2, and is the second-largest ice shelf on the Antarctic Peninsula14. It is a slow-moving ice shelf. George VI Ice Shelf is melting rapidly at its base12, and is largely sustained by snow accumulation. George VI Ice Shelf is currently receding at a rate of 1 to 1.1 kilometres per year, and it is thinning, and the grounding line is retreating14. Frontal recession generally occurs as series of large calving events following the development of rifting.
You can read more about George VI Ice Shelf in this blog post.
1. Cook, A.J. & Vaughan, D.G. Overview of areal changes of the ice shelves on the Antarctic Peninsula over the past 50 years. The Cryosphere 4, 77-98 (2010).
2. Glasser, N.F., Scambos, T.A., Bohlander, J.A., Truffer, M., Pettit, E.C. & Davies, B.J. From ice-shelf tributary to tidewater glacier: continued rapid glacier recession, acceleration and thinning of Röhss Glacier following the 1995 collapse of the Prince Gustav Ice Shelf on the Antarctic Peninsula. Journal of Glaciology 57, 397-406 (2011).
3. Davies, B.J., Carrivick, J.L., Glasser, N.F., Hambrey, M.J. & Smellie, J.L. Variable glacier response to atmospheric warming, northern Antarctic Peninsula, 1988–2009. The Cryosphere 6, 1031-1048 (2012).
4. Shepherd, A., Wingham, D., Payne, T. & Skvarca, P. Larsen ice shelf has progressively thinned. Science 302, 856-859 (2003).
5. Fricker, H.A. & Padman, L. Thirty years of elevation change on Antarctic Peninsula ice shelves from multimission satellite radar altimetry. Journal of Geophysical Research: Oceans 117, C02026 (2012).
6. Domack, E., Duran, D., Leventer, A., Ishman, S., Doane, S., McCallum, S., Amblas, D., Ring, J., Gilbert, R. & Prentice, M. Stability of the Larsen B ice shelf on the Antarctic Peninsula during the Holocene epoch. Nature 436, 681-685 (2005).
7. De Angelis, H. & Skvarca, P. Glacier surge after ice shelf collapse. Science 299, 1560-1562 (2003).
8. Reynolds, J.M. The structure of Wordie Ice Shelf, Antarctic Peninsula. British Antarctic Survey Bulletin 80, 57-64 (1988).
9. Doake, C.S.M. & Vaughan, D.G. Rapid disintegration of the Wordie Ice Shelf in response to atmospheric warming. Nature 350, 328-330 (1991).
10. Braun, M., Humbert, A. & Moll, A. Changes of Wilkins Ice Shelf over the past 15 years and inferences on its stability. The Cryosphere 3, 41-56 (2009).
11. Padman, L., Costa, D.P., Dinniman, M.S., Fricker, H.A., Goebel, M.E., Huckstadt, L.A., Humbert, A., Joughin, I., Lenaerts, J.T.M., Ligtenberg, S.R.M., Scambos, T. & van den Broeke, M.R. Oceanic controls on the mass balance of Wilkins Ice Shelf, Antarctica. Journal of Geophysical Research: Oceans 117, C01010 (2012).
12. Rignot, E., Jacobs, S., Mouginot, J. & Scheuchl, B. Ice Shelf Melting Around Antarctica. Science (2013).
13. Morris, E.M. & Vaughan, A.P.M. Spatial and temporal variation of surface temperature on the Antarctic Peninsula and the limit of viability of ice shelves. in Antarctic Peninsula climate variability: historical and palaeoenvironmental perspectives, Vol. Volume 79 (eds. Domack, E.W., Leventer, A., Burnett, A., Bindschadler, R., Convey, P. & Kirby, M.) 61-68 (American Geophysical Union, Antarctic Research Series, Volume 79, Washington, D.C., 2003).
14. Holt, T.O., Glasser, N.F., Quincey, D. & Siegfried, M.R. Speedup and fracturing of George VI Ice Shelf, Antarctic Peninsula. The Cryosphere 7, 797-816 (2013).